There is a need for absorbable braided sutures with improved performance. In particular, these sutures should have high initial tensile strength, prolonged strength retention in vivo, good knot security and tie down (with a small knot bundle), good handling characteristics, and be biocompatible. The braided sutures should also have a low tissue drag that minimizes trauma to the sutured tissues. Biocompatible braided polyhydroxyalkanoate (“PHA”) sutures, or those having a braided component, can be made with high tensile strength, prolonged strength retention in vivo, and good knot security; however, it would be advantageous if the tissue drag resulting from the braided structure of the suture could be reduced.
A number of different types of coatings have been applied to braided sutures to lower tissue drag. These coatings must: impart good lubricity to the fiber/braid, have a reasonable shelf life, be biocompatible, and be compatible with the physical and chemical structure of the fiber. For example, the coating must not react with the suture fiber, dissolve the fiber, or adversely alter the mechanical and thermal properties of the fiber. Thus, it is desirable to identify coatings that can be applied to PHA braided sutures to reduce tissue drag by imparting good lubricity to the braid and fill the braid interstices without adversely altering the inherent properties of the fiber/braid. Moreover, it is particularly desirable to identify coatings that can be applied to braided sutures, or sutures containing braided components, made from P4HB polymers and copolymers thereof.
In addition to providing coatings for PHA fibers that reduce tissue drag, it is desirable to identify spin finishes that can be applied to PHA fibers to facilitate their manufacture and, optionally, their conversion to other products, including medical textiles. Spin finishes are applied during extrusion of multifilaments to keep the fiber bundle protected and intact, and to impart lubricity to the fiber bundle so that it may be manipulated in subsequent processing steps without damaging the fiber. Spin finishes are also applied to monofilament to facilitate textile processing without damaging the fiber. Spin finishes for medical applications must satisfy a number of conditions. These include compatibility with the fiber (similar to that described for suture coatings), and effectiveness under the process conditions, for example, in processes such as spinning and orienting of the fiber, and in knitting or weaving of the fiber. In addition, it must be easy to apply the spin finish, and easy to remove the spin finish without damaging the fiber or adversely impacting any component in the fiber such as dye, using conditions that are compatible with the fiber's subsequent use in a medical device. Residues of the spin finish should also be easily detectable, and any spin finish left on the device, even residues, needs to be biocompatible. The spin finish should also be stable with a long shelf life, and any spin finish left on the final product should not adversely impact the properties or the shelf life of the final product.
It is also desirable to provide multifilament with a lower denier per filament (dpf) and improved tenacity compared to uncoated multifilament. Such fibers can be used to prepare higher strength medical devices as well as reduce the device profile.
It is an object of the present invention to provide methods to produce coated PHA braids for use as sutures and in other medical devices, wherein the coating provides the device with good lubricity to minimize trauma to tissues, and good knot strength (in the case of a suture), without adversely impacting the properties of the PHA polymer.
It is a further object of the present invention to provide processes to produce PHA multifilament fiber using spin finish, and process PHA monofilament and multifilament fibers into other forms, such as textiles, with the aid of spin finish such that the fibers may be processed without damage, and the spin finish imparts lubricity to aid in the subsequent processing of the fiber.
It is another object of the present invention to provide coated PHA multifilament and monofilament fibers, coated PHA braided sutures, coated PHA braided structures as components of other devices, and other coated PHA medical devices and textiles, including monofilament and multifilament knitted and woven meshes, and vascular grafts, which are biocompatible and can be used in medical applications, for example, as implants for soft tissue repair and reconstruction, temporary wound support, cosmetic, breast, facial, and plastic surgery, and for the regeneration and replacement of tissues. Such devices and textiles may be further coated or encapsulated by or contain collagen.
It is yet another object of the invention to provide PHA multifilament fibers with low filament denier and higher tenacity.
It is still another object of the invention to provide coatings and spin finishes that can be used in processing PHA polymers to yield materials with excellent physical and mechanical properties, and biocompatibility.